WO1990005060A1

WO1990005060A1 - Device for welding plastic films

Info

Publication number: WO1990005060A1
Application number: PCT/EP1989/001271
Authority: WO
Inventors: Karlheinz SCHÄFER; Paul Reinheimer; Bernd Ellenberger; Karl Christoph Herzer; Gerhard Lass
Original assignee: G.M. Pfaff Aktiengesellschaft
Priority date: 1988-11-08
Filing date: 1989-10-25
Publication date: 1990-05-17
Also published as: JPH04505730A; CA2002419A1; DE3921711C1; EP0442919B1; EP0442919A1; JP2582448B2

Abstract

To obtain a device for welding plastic films which is light, compact and easy to operate, the two pressure rollers (40, 47) are driven by a single motor (19) arranged inside the transverse part (4) of a U-shaped housing (1) or inside a tubular pressure element (135) of a pressure mechanism (136), which runs parallel to and at a distance from the transverse part (103). The welding device is particularly suitable for welding operations carried out in a vertical plane or overhead, for example when lining tunnels.

Description

description

Device for welding plastic films

The invention relates to a device for welding plastic films according to the preamble of claim 1.

From DE-GM 8301 191 a welding device with an essentially U-shaped housing is known, in which a cantilevered pressure roller is arranged at the ends of the two housing arms lying in different planes and changeable in their mutual angular position. The pinch rollers are connected to their own motor via corresponding gears or to a common motor via disengageable clutches. The welding device has two pairs of rollers for support against the lower of the two plastic films to be welded to one another or against the base.

DE-0S 35 35 760 is another mobile

Welding device with an essentially U-shaped housing is known, in which rollers are dispensed with to save weight. In this welding device, each of the pressure rollers arranged at the end of each housing arm is also assigned its own motor and its own reduction gear. The motors and gears are arranged coaxially with the corresponding pressure rollers. Since the motors protrude laterally from the housing arms, the welding device is bulky and unwieldy.

The invention has for its object to provide a mobile device for welding plastic films, which is not only as light as possible, but also compact built and is therefore particularly handy. The object is achieved by the characterizing features of claim 1.

The measure of arranging on the web part of the U-shaped housing a gear motor which serves to drive both pressure rollers and which has two mutually opposite outputs, which are each connected to the associated pressure roller via a gear, results in a weight reduction on the one hand and a motor saving on the other achieved a compact construction by avoiding parts protruding laterally over the housing. As a result of these two advantageous properties, the welding device designed according to the invention is particularly suitable for the production of tunnel linings in which the entire weight of the welding device has to be carried by the operator during welding on vertical walls or overhead. The use of a single motor for both pressure rollers has the further advantage that the pressure rollers always run synchronously with one another.

An even more space-saving design can be achieved according to claim 2 in that the geared motor is arranged within the tubular, circumferentially closed web part, whereby the additional advantage is achieved that the geared motor is encapsulated and thus protected against contamination and damage.

By the measure specified in claim 10, the drive motor for the pressure rollers in a tubular, spaced parallel to the web part of the U-shaped housing arranged pressure member of the pressure mechanism and the

To divide the drive movement of the motor with the aid of a shaft mounted in the web part between the two gears connected to the pressure rollers, it is possible to use a gear motor with only one output as the drive motor. A geared motor with only one output is around the length of the saved gear narrower, which makes it possible to make the housing of the device, ie the web part and the pressure member correspondingly narrower. Even if the weight saving due to the elimination of one gear of the geared motor is compensated for by the now required shaft in the web part and the additional gear connecting this shaft to the geared motor, the reduction in the length of the web part, the pressure member and the mounting of the Pressure rollers a noticeable further weight reduction of the entire device.

Of even greater importance, however, is the advantage that, by reducing the width of the housing, the device is much narrower and therefore more compact overall and consequently considerably more manageable.

The developments according to claims 11 and 12 also achieve a comparatively flat design of the device, and. in particular in that the actuating lever can be adjusted into a position essentially parallel to the housing arm supporting it after the arms have been pivoted into the working position.

Further advantageous embodiments of the welding device are specified in the other subclaims.

The invention is explained using three exemplary embodiments shown in the drawing. It shows: ^"

Figure 1 is a plan view of the welding device.

Fig. 2 is a sectional view along line II-II of Fig. 1;

Fig. 3 is a sectional view along line III-III of Fig. 1; Fig. 4 is a plan view of the welding device of the second embodiment;

5 is a view of the welding device;

6 is a side view of the welding device;

Fig. 7 is a sectional plan view of the

Welding device of the third embodiment;

8 is a partially sectioned side view of the welding device;

Fig. 9 is a side view of the pressure arm clamped on the pressure member and

10 is a sectional view of an actuating mechanism for the pressure arm according to line IV-IV of FIG. 2nd

Embodiment 1

The welding device shown in Figures 1 to 3 has a substantially U-shaped housing 1, which consists of two arms 2 and 3 and a web part 4 connecting them. The arms 2, 3 are hollow and each have a removable side wall 5, 5.

The web part 4 is formed by two telescopically nested bearing sleeves 7, 8, of which the outer bearing sleeve 7 with the arm 2 and the inner bearing sleeve 8 is firmly connected to the arm 3. The inner bearing sleeve 8 consists of a ring part 9, a pipe section 10 and an elongated hub 11, these parts being firmly connected to one another by welding. The hub 11 has a flange 12, a base part 13 with a relatively thick wall and an extension 14. At one end of the outer bearing sleeve 7 is a stepped shoulder 15 and at the other end cylindrical approach 16 formed.

The shoulder 16 of the outer bearing sleeve 7 rests on the hub 11 and forms a bearing 17 together with the latter. On the shoulder 14 of the hub 11 a grooved ball bearing 18 is arranged, on which the shoulder 15 of the outer bearing sleeve 7 is supported. The two bearing sleeves 7, 8 are rotatably supported on one another via the bearings 17, 18, as a result of which the arms 2, 3 can also be rotated relative to one another.

A known geared motor 19 is arranged within the bearing sleeve 8 and consists of a centrally arranged motor part 20 and two external planetary gears 21, 22. Each planetary gear 21, 22 has a shaft 23 and 24 on the output side. The geared motor 19 is connected in a rotationally fixed manner to the inner bearing sleeve 8 via a bearing plate 25, in that the planetary gear 22 is screwed to the bearing plate 25 and this is screwed to the ring part 9. The other end of the geared motor 19 is supported in a bearing plate 26, which is screwed to the planetary gear 21 and is supported radially with a shoulder (not shown in more detail) on the shoulder 14 of the hub 11. The end shield 26 presses with a shoulder 27 against the inner ring of the ball bearing 18 and thereby on the one hand holds the outer ring of the ball bearing 18 in contact with an unspecified shoulder of the shoulder 15 of the outer bearing sleeve 7 and on the other hand causes the end face of the shoulder 16 to bear against the flange 12th

A toothed belt pulley 28 is fastened on the shaft 23, over which a toothed belt 29 runs. The toothed belt 29 also runs over a toothed belt pulley 30 which is fastened on a shaft 31 which is mounted in a floating manner in the arm 2. A gear 32 is also fastened on the shaft 31, which meshes with a gear 34 attached to a shaft 33 which is also mounted on the fly. A toothed belt pulley 35 is also fastened on the shaft 33, via which a toothed belt 36 runs. The toothed belt 36 also runs over a toothed belt pulley 37 which is attached to one end of a shaft 38. The wave 38 is accommodated in a bearing sleeve 39 fastened to the arm 2 and carries at its other end a pressure roller 40 which is firmly connected to it. The two gear wheels 32, 34 form a reversing gear 41.

A toothed belt pulley 42 is fastened on the shaft 24, over which a toothed belt 43 runs. The toothed belt 43 also runs over a toothed belt pulley 44 which is attached to the end of a shaft 45. The shaft 45 is received in a bearing sleeve 46 fastened to the arm 3 and carries at its other end a pressure roller 47 firmly connected to it.

On the arm 3, an electrically heated heating wedge 49 is arranged with the aid of a parallel crank mechanism 48, which can be moved back and forth by a hand lever 50 connected to the parallel crank mechanism 48 between the retracted rest position shown in FIG. 1 and a working position located close to the pressure rollers 40, 47 is.

In the base part 13 of the hub 11, two spring bars 51 running parallel to one another are fastened, which protrude through a recess 52 in the outer bearing sleeve 7 and extend essentially along the arm 2. The two spring bars 51 are encompassed by two opposing double professional rollers 53, 54, which are freely rotatably mounted on a first carrier plate 55. The first carrier plate 55 is arranged with the aid of vertically extending elongated holes 56 and corresponding screws 57 on a second carrier plate 58 so as to be adjustable transversely to the longitudinal axis of the spring bars 51. The second support plate 58 is made with the aid of horizontally extending elongated holes 59 and corresponding ones

Screws 60 on a holding plate 61 in parallel! arranged adjustable to the longitudinal axis of the spring bars 51. The holding plate 61 is arranged fixedly on the arm 2 with the interposition of a spacer 62 and has a multiplicity of bores 63, as a result of which the carrier plate 58 is spaced one or more bores apart Holding plate 61 can be moved. The components 51 to 62 form a pressure mechanism 64.

Triangular runners 65, 66 rounded at the projecting tip are arranged on the ends of the arms 2, 3 adjacent to the web part 4.

Functionality:

The welding device is used to produce lap seams on plastic films, in particular when lining tunnels, in which the weld seams are mainly to be carried out in a vertical plane and overhead.

The welding device is arranged between the plastic films to be welded to one another in such a way that one

Plastic film runs below the web part 4 and the heating wedge 49 and the other plastic film runs above the web part 4 and the heating wedge 49, whereupon they lie directly on top of one another between the pressure rollers 40, 47.

The welding pressure between the pressure rollers 40, 47 required to carry out the welding process is brought about by the pressure mechanism 64. With a corresponding setting of the two support plates 55, 58, the two spring bars 51 are tensioned downward according to FIG a torque is exerted which causes the upper pressure roller 47 to be pressed against the underlying pressure roller 40.

With the pressure mechanism 64, two different basic settings can be made, namely on the one hand the size of the prestressing force and on the other hand the height of the spring stiffness of the spring bars 51 the spring bars 51 are adjusted to move the carrier plate 55. The spring stiffness of the spring bars 51 can be adjusted by displacing or displacing the support plate 58 parallel to the longitudinal axis of the spring bars 51, the effective length of the spring bars 51 being changed.

The two different setting options of the pressure mechanism 64 make it possible to set the optimum working conditions for certain film materials and film thicknesses. So z. B. when welding HDPE films a relatively high pressure is necessary. At the same time, in addition to the high pretension, a high degree of spring stiffness is also desirable, so that contaminants such as e.g. B. grains of sand and small stones that accidentally get between the pressure rollers 40, 47, are pressed into the softened film, so that the necessary welding pressure is maintained even at these points. If, however, larger transitions, such as. B. cross seams are to be run over, a relatively small spring stiffness is set at high preload so that the preload does not have to be reduced when driving over the transitions.

If a particularly low welding pressure is required, only one spring rod 51 can be used. If, on the other hand, an extremely high welding pressure is necessary, spring bars with a larger cross-section can be used.

Since the entire pressure mechanism 64 according to FIG. 2 does not protrude beyond the top and bottom of the arm 2 carrying it, the entire welding device is very compact and very handy.

After the welding pressure has been set, the heating wedge 49 heated to the required welding temperature is introduced into the welding position. As soon as the heating wedge 49 has reached the welding position, the gear motor 19 switched on, whereupon the welding device moves with the aid of the driven pressure rollers 40, 47 relative to the foils, the softened foil regions being connected to one another to form a weld seam.

Embodiment 2

The welding device shown in FIGS. 4 to 6 is identical to the welding device of the first exemplary embodiment with regard to the housing and the drive device. The essentially U-shaped housing 1 also consists of the two arms 2, 3 and a web part 4 which connects them in an articulated manner, in which the geared motor for the pressure rollers 40, 47, which is not shown in this case, is arranged. The welding device also has a heating wedge 49 arranged on a parallel crank mechanism 48.

Furthermore, the arms are adjacent to the web part 4 ends

2, 3 triangular, rounded at the projecting tip

Skids 65, 66 attached.

On the other hand, the pressure mechanism 80 used to generate the welding pressure is constructed completely differently from the pressure mechanism 64 of the first exemplary embodiment. The pressure mechanism 80 has a rod-shaped pressure member 81 fastened to the runner 65 of the arm 2, which extends at a distance from the web part 4 parallel to its longitudinal axis. At the free end of the pressure member 81, an angle piece 82 is attached, which has an L-shaped horizontal leg plate 82a. The pressure member 81 and the elbow 82 together form a pressure beam 83. In an image captured in the blade 66 rotating piece 84, a threaded spindle 85 is fixed, which projects through a bore 86 of the runner 66, a not ^'bore the leg plate 82a and shown. On the part of the threaded spindle 85 located above the leg plate 82a, a handle 87 and a plurality of plate springs 88 are arranged, which are located on the leg plate 82a via a washer 89 support. The components 85, 87, 88 and 89 form a spring mechanism 90. Below the leg plate 82a, a height-adjustable stop disk 91 with a corresponding internal thread is arranged on the threaded spindle 85.

On the arm 3, an angle bracket 92 is attached, on which a longitudinal and a transverse to the arms 2, 3 handle 93 and 94 is fixed. In the angle bracket 92, a longitudinally displaceable rod 95 is received, the lower end of which carries a pressure piece 96 and which is further connected to a toggle lever gear 98 having a handle 97. The components 92 and 95 to 98 form an actuating mechanism 99.

How it works: Except for the setting of the welding pressure, the rest

Operation of the welding device is the same as that of the welding device according to the first exemplary embodiment, so that it is not necessary to go into this in more detail.

The level of the welding pressure is set using the handle 87. By turning the handle 87 downward, the plate springs 88 are pressed more strongly against the leg plate 82a and thus the pressure beam 83 is pressed downward as a whole. The pressing force acting on the pressure beam 83 has the effect that a torque acting clockwise as shown in FIG. 6 is exerted on the skid 65. Due to this torque, the arm 2 is pivoted clockwise as shown in FIG. 6, whereby the pressure roller 40 is pressed upwards against the pressure roller 47.

The common angle between the arms 2, 3 in the welding position can be limited by the stop disc 91, ie the arms or the pressure rollers 40, 47 can no longer be moved towards one another when the leg plate 82a rests on the stop disc 91. In this way, the thickness of the weld seam to be produced can be set exactly. With the aid of the adjusting mechanism 99, the arms 2, 3 can be moved away from one another, whereupon two new foils can be inserted between the pressure rollers 40, 47 without hindrance. For this purpose, the handle 97 is pivoted downward, thereby also moving the rod 95 downward. In the course of this movement, the pressure piece 96 abuts on the leg plate 82a which is supported on the stop disc 91 and causes the pressure beam 83, which in this case acts as a two-armed lever, to be pivoted overall about the stop disc 91, which now serves as the axis of rotation, this pivoting movement according to FIG. 4 counterclockwise. The pivoting movement leads to an elastic bending of the pressure member 81 which is fixedly connected to the runner 65, as a result of which a torque acting counterclockwise as shown in FIG . As soon as this torque is stronger than the oppositely directed torque generated by the spring mechanism 90, the arm 2 is pivoted counterclockwise according to FIG. 6, as a result of which the pressure roller 40 moves away from the pressure roller 47.

Embodiment 3

The welding device has an essentially U-shaped housing 100, which consists of two arms 101 and 102 and a web part 103 connecting them to one another. The arms 101, 102 are hollow and each have a removable side wall 104, 105.

The web part 103 is formed by two telescopically nested bearing sleeves 106, 107, of which the outer bearing sleeve 106 is fixed to the arm 102 and the inner bearing sleeve 107 to the arm 101. The outer bearing sleeve 106 is rotatably supported on the inner bearing sleeve 107 via two needle bearings 108, 109, as a result of which the arms 101, 102 can also be rotated relative to one another. The needle bearing 108 is supported on one side on a shoulder 110 of the inner bearing sleeve 107 and on the other side on a locking ring 111 arranged in the outer bearing sleeve 106. The needle bearing 109 is supported on one side on a locking ring 112 arranged in the inner bearing sleeve 107 and on the other side on a bearing plate 113 screwed onto the arm 102.

A continuous shaft 115 is supported in two bearing bushes 114 of the inner bearing sleeve 107. On the end of the shaft 115 extending into the arm 101, a toothed belt pulley 116 and a toothed wheel 117 are attached immediately adjacent, which abuts laterally on the inside of the arm 101. On the other end of shaft 115, which extends into arm 102, a toothed belt pulley 118 is attached, which rests laterally on end plate 113. The toothed belt pulleys 116, 118 fastened on the shaft 115 and the gearwheel 117 form an axially acting holder for the arms 101, 102.

The gearwheel 117 meshes with a gearwheel 119 which is fastened on a shaft 120 which is mounted in a floating manner in the arm 101. On the shaft 120, a toothed belt pulley 122 is also fastened, over which a toothed belt 123 runs. The toothed belt 123 also runs over a toothed belt pulley 124 which is attached to the end of a shaft 125. The shaft 125 is received in a bearing sleeve 126 fastened to the arm 101 and carries at its other end a pressure roller 127 firmly connected to it. The components 117, 119 to 124 together form a first gear 128 which reverses the direction of rotation.

A toothed belt 129 runs over the toothed belt pulley 118 and is also fastened via a shaft 130 attached to the end

Toothed belt pulley 131 runs. The shaft 130 is received in a bearing sleeve 132 fastened to the arm 102 and carries at its other end a pressure roller 133 which is firmly connected to it. The components 118, 129 and 131 together form a second gear 134 which maintains the direction of rotation. A tubular pressure member 135 is attached to the end region of the arm 101 opposite the pressure roller 127 and is a component of a pressure mechanism 136 explained in more detail below. There is a known one on arm 101

Fixed gear motor 137, which extends within the pressure member 135, but without touching it. The geared motor 137 consists of a motor part 138 and a laterally flange-mounted planetary gear 139. The planetary gear 139 has a shaft 140 which forms an output of the gear.

A toothed belt pulley 141 is fastened on the shaft 140, over which a toothed belt 142 runs. The toothed belt 142 also runs over the toothed belt pulley 116 already described. The components 116, 141, 142 together form a gear 143 which drives the output of the planetary gear 139 to the shaft 115.

A pressure arm 144 is non-rotatably clamped on the pressure member 135, which, according to FIG. 3, consists of a slotted clamping sleeve 145, a square hollow profile, which extends above the arm 102, extends parallel to the arm 146, and an extension 147 extending transversely thereto consists.

A narrow support plate 148 is attached to the end of the arm 102 opposite the pressure roller 133. A threaded spindle 150 is pivotably arranged on the carrier plate 148 with the aid of a collar screw 149 and projects through a bore 151 in FIG. 3 provided in the projection 147. On the part of the threaded spindle 150 located above the extension 147, a handle 152 and a large number of disc springs 153 are arranged, which are supported on the extension 147 via a washer 154. The components 150, 152, 153 and 154 together form a spring mechanism 155.

Below the shoulder 147 is one on the threaded spindle 150 Appropriate internal thread provided height adjustable stop disc 156 is arranged.

A bracket 157 with a U-shaped cross section is attached to the arm 102, into which the bracket 146 projects. In the bracket 157, a shaft 159 is mounted above a flat extension 158 of the bracket 146, which has a collar 160 at one end and carries a clamping ring 161 at the other end. An eccentric 162 is fastened on the shaft 159 and cooperates with the extension 158 of the boom 146. An actuating lever 163 is rotatably mounted on the shaft 159 in addition to the eccentric 162. A pin 164 projecting laterally in the direction of the eccentric 162 is fixedly arranged in the actuating lever 163. In the eccentric 162, a plurality of bores 165 are provided, the diameter and radial distance of which from the shaft 159 are dimensioned such that the pin 164 can engage in them. A compression spring 166 arranged on the shaft 159 holds the actuating lever 163 in contact with the eccentric 162. The pin 164, the bores 165 and the compression spring 166 together form a disengageable clutch. In the ^'console 157 a recess 167 is above the eccentric 162, which makes it possible that the actuating lever can be pivoted in a direction perpendicular to the arm 102 position 163rd The components 159 to 166 together form an actuating mechanism 168.

An electrically heated heating wedge 170 is arranged on the arm 102 with the aid of a parallel crank mechanism 169, which is connected by a hand lever 171 connected to the parallel crank mechanism 169 between a rest position remote from the pressure rollers 127, 133 and the one shown in FIG. 1, close to the pressure rollers 127, 133 located working position can be moved back and forth.

Functionality:

The welding device is used to produce lap seams on plastic films, in particular when lining tunnels, where the welds are mainly to be carried out in a vertical plane and overhead.

The welding device is arranged between the plastic films to be welded to one another in such a way that one plastic film runs below the web part 103 and the heating wedge 170 and the other plastic film runs above the web part 103 and the heating wedge 170, whereupon they lie directly on top of one another between the pressure rollers 127, 133 .

The welding pressure between the pressure rollers 127, 133 required for carrying out the welding process is brought about by the pressure mechanism 136.

The level of the welding pressure is set using the handle 152. By turning the handle 152 downward, the plate springs 153 are pressed more strongly against the projection 147, as a result of which the pressure member 135 is pressed downward. The pressing force acting on the pressure member 135 causes a torque acting clockwise according to FIG. 2 to be exerted on the arm 101.

Due to this torque, the arm 101 is pivoted clockwise according to FIG. 2, whereby the pressure roller 127 is pressed upwards against the pressure roller 133.

The common angle between the arms 101, 102 in the welding position can be limited by the stop disc 156, i. H. the arms or the pressure rollers 127, 133 can no longer be moved towards one another when the shoulder rests on the stop disc 156. In this way, the thickness of the weld seam to be produced can be set exactly.

With the aid of the adjusting mechanism 168, the arms 101, 102 can be moved away from one another, whereupon two new foils can be inserted unhindered between the pressure rollers 127, 133. For this purpose, the operating lever 163 from the one in FIG. 2 shown position pivoted upwards. The eccentric 162, which is also rotated via the pin 164, pivots the boom 146 counterclockwise, the pressure arm 144 being supported on the stop disc 156 with the attachment 147. Since the pressure member 135 and the pressure arm 144 are firmly connected to one another and thus form a coherent pressure bar 172 b, the actuating movement emanating from the adjusting mechanism 168 has the effect that the pressure bar 172, which in this case is supported as a two-armed lever, altogether around the stop disc 156, which now serves as the axis of rotation is pivoted. The pivoting movement leads to an elastic bending of the pressure member 135 which is fixedly connected to the arm 101, as a result of which a torque is exerted on the arm 101. As soon as this torque is stronger than the counter-clockwise torque generated by the spring mechanism 155, the arm 101 is pivoted counterclockwise according to FIG. 2, as a result of which the pressure roller 127 moves away from the pressure roller 133.

Claims

1. Device for welding plastic films with a substantially U-shaped housing which is formed by two arms and a web part connecting them to one another, the arms being pivotable relative to one another about the longitudinal axis of the web part, each with one at the free end of each Poorly arranged driven pressure roller, a pressure mechanism for pressing the pressure rollers onto one another and a heating element, characterized in that a gear motor (19) serving to drive both pressure rollers (40, 47) is arranged on the web part (4) and has two outputs (23, 24), which, with the interposition of one gear (28 - 37 or 42 - 44), drive the two pressure rollers (40; 47) in opposite directions.

2. Device according to claim 1, characterized in that the geared motor (19) is arranged within the tubular, circumferentially closed web part (4). ^{~ ■}

3. Apparatus according to claim 2, characterized in that the web part (4) consists of two telescopically inserted into each other, with one of the two arms (2, 3) firmly connected bearing sleeves (7, 8), of which the inner bearing sleeve (8th ) is rotatably connected to the geared motor (19).

4. The device according to claim 3, characterized in that the inner bearing sleeve (8) over the entire length of the geared motor (19) and the outer bearing sleeve (7) extends at least to the middle of the inner bearing sleeve (8) and that the two bearing sleeves (7, 8) are supported on one another via two bearings (17, 18), the mutual spacing of which is essentially that. Length of the outer bearing sleeve (7) corresponds.

5. Apparatus according to claim 3 and 4, characterized in that the inner bearing sleeve (8) as a carrier for at least one through a recess (52) of the outer bearing sleeve (7) protruding and substantially parallel to the relative to the geared motor (19) movable Arm (2) extending spring rod (51) of a pressure mechanism (64) is used, which has a pressure piece (53, 54) arranged on the arm (2) and interacting with the spring rod (51).

6. The device according to claim 5, characterized in that the pressure piece is formed by at least one on the spring rod (51) supporting roller (53) which for changing the effective length of the spring rod (51) along the arm (2) carrying it and to change the bias of the spring bar (51) transverse to the arm (2) is adjustable.

7. The device according to one or more of claims 1 to 4, characterized in that one of the arms (2) serves as a holder for a - arranged at a distance from the web part (4), parallel to the longitudinal axis of the pressure member (81), the one Is part of a pressure bar (83) of a pressure mechanism (80), and that the pressure bar (83) can be acted upon by an adjustable spring mechanism (90) supported on the other arm (3).

8. The device according to claim 7, characterized in that a stop element (91) is arranged on the side of the pressure beam (83) opposite the spring mechanism (90) and that the free end of the pressure beam (83) around the stop element (91) pivoting adjusting mechanism (99) is assigned.

9. The device according to claim 8, characterized in that the stop element (91) for limiting the pivoting angle of the arms in the working position (2, 3) is adjustable.

10. Device for welding plastic films with a substantially U-shaped housing which is formed by two arms and a web part connecting them to one another, the arms being pivotable relative to one another about the longitudinal axis of the web part, each with one at the free end of each Armes arranged driven pressure roller, one

Pressure mechanism which has a rod-shaped pressure element arranged on one of the arms at a distance from the web part, essentially parallel to its longitudinal axis, and a spring mechanism which cooperates with it and is supported on the other arm, and with a heating element, the housing being used to drive both pressure rollers Serving geared motor is arranged, which is connected via a first gear that reverses the direction of rotation and a second gear that maintains the direction of rotation to the respectively assigned “pressure roller”, characterized in that the pressure member (135) is of tubular design and has only one output (shaft 140). provided geared motor (137) within the pressure member (135) and the output (shaft 140) of the geared motor (137) via an additional gear (143) and a shaft (115) mounted within the web part (103) with the first and second gears (128, 134) is connected.

11. The device according to claim 10, characterized in that the pressure member (135) carries a transversely projecting non-rotatably arranged pressure arm (144) which is on a stop element

(Stop disc 156) of the spring mechanism (155) is supported and extends above the arm (102) of the housing (100) which is not connected to the pressure member (135) and that the free end (extension 158) of the pressure arm (144) is one of a rotatable one Eccentric (162) and an actuating lever (163) formed adjusting mechanism (168) is assigned.

12. The apparatus according to claim 11, characterized in that the actuating lever (163) is connected to the eccentric (162) via a disengageable clutch (164, 165-, 166) having a plurality of positions.